1. (Field of the Invention)
The present invention relates to a light-receiving device, e.g. a PD (photo diode) array and a Schottky diode array having a plurality of light-detecting regions formed on a semiconductor material, and an optical connector using the same and, more particularly, to a light-receiving device which can minimize crosstalk among light-detecting regions, and an optical connector using the same.
2. (Related Background Art)
In the field of optical communication, parallel signal transmission using a plurality of parallel optical fibers has been attempted to realize a large-capacity communication system using conventional PDs and LDs. From this point of view, development of integrated PDs and LDs used in parallel signal transmission has been expected.
As an integrated optical device of this type, PD arrays having sectional structures shown in FIGS. 9A, 9B, and 9C have been proposed.
In a PD array shown in FIG. 9A, semiconductor crystals 2a, 2b, and 2c of a first conductivity type are grown on a substrate 4, and an impurity is selectively diffused in semiconductor crystals 2b and 2c to form regions 1 of a second conductivity type, thus forming PIN-PD structures serving as light-detecting regions (e.g., Society of Electronic Information Communications, national spring meeting, 1988, C-352).
In the device having the structure shown in FIG. 9A, however, light incident on a portion between adjacent light-detecting regions is absorbed by the absorption layer 2b, and an electric charge is generated in this region. The electric charge generated in the absorption layer 2b is diffused in a lateral direction, and is undesirably flowed into the region 1 of the second conductivity type. Accordingly, a current flows into the PIN-PD structure from the absorption layer, thus posing the following problems: (1) an electric charge generated outside a light-detecting region is superposed on a signal current and causes crosstalk; and (2) a response time of an array is prolonged by a diffusion current having a low response speed.
In a PD array having a structure shown in FIG. 9B, semiconductor crystals 2a, 2b, and 2c of a first conductivity type are grown on a semiinsulating substrate 3, and light-detecting regions are then formed in the same manner as in FIG. 8A. Subsequently, a portion of the semiconductor crystals 2a, 2b, and 2c between adjacent light-detecting regions is removed until the semiinsulating substrate 3 is exposed (e.g., Society of Electronic Information Communications, national fall meeting, 1989, C-225).
In the PD array having the structure shown in FIG. 9B, because of partial etching of the semiconductor crystals 2a, 2b, and 2c, lateral diffusion of an electric charge can be prevented, and the above-mentioned problems can be solved. However, since steps are inevitably formed on the surface of the PD array, such structure causes errors occurring due to a non-flat surface during a fabrication process (e.g., photolithographic errors), or a structure of a device protective film may become incomplete.
In a PD array having a structure shown in FIG. 9C, after light-detecting regions 1 of a second conductivity type are formed in semiconductor crystals 2a, 2b, and 2c of a first conductivity type in the same manner as in FIG. 9A, a metal film 12 is formed on the surface of the semiconductor crystal 2a between the adjacent light-detecting regions.
In the PD array having the structure shown in FIG. 9C, since the metal film 12 is formed on the surface of the semiconductor crystal 2c to shield incidence of stray light on a portion outside the light-detecting regions, crosstalk caused by lateral diffusion of an electric charge can be prevented. However, incident light is multiple-reflected between the surface of the metal film 12 and a surface of an optical fiber connector 13, and stray light is undesirably transmitted to an adjacent light-detecting region. Thus, the stray light incident on the adjacent light-detecting region often causes crosstalk.